1. Field of the Invention
The present invention relates to a method for preventing and/or treating Type I diabetes (insulin dependent diabetes mellitus) by the administration of at least one of the following: (i) gamma interferon, (ii) an analog of gamma interferon, or (iii) an inducer of gamma interferon.
The present invention is further directed to a method for preventing and/or treating recurrent Type I diabetes, e.g., in transplant subjects having islet or pancreatic transplants.
2. Background of the Invention
Type I diabetes mellitus, also referred to as insulin-dependent diabetes mellitus (IDDM), is a common endocrine disorder in childhood. About 30% to 40% of diabetic children will eventually develop nephropathy requiring dialysis and transplantation. Other significant complications include cardiovascular disease, stroke, blindness and gangrene. Moreover, diabetes mellitus accounts for a significant proportion of morbidity and mortality among dialysis and transplant patients.
Type I diabetes mellitus is an autoimmune disorder, the onset of which results from a well-characterized insulitis. During this condition, the inflammatory cells are apparently specifically directed against the beta cells of the pancreatic islets.
These inflammatory cells are predominantly T cells and a smaller percentage are macrophages which are not specifically directed. The mononuclear cells are closely associated with degenerating beta cells, but are absent when there are no beta cells contained in the islets. Moreover, the infiltrate is specifically directed against the beta cells. However, other endocrine cells within the islets, specifically glucagon-containing alpha cells and somatostatin producing delta cells remain undamaged.
It has been demonstrated that a large proportion of the infiltrating T lymphocytes produced during Type I diabetes mellitus are CD8-positive cytotoxic cells, which confirms the cytotoxic activity of the cellular infiltrate. CD4-positive lymphocytes are also present, the majority of which are helper T cells (Bottazzo et at., 1985, New England Journal of Medicine, 313, 353-359). The infiltrating cells also include lymphocytes or B cells that produce immunoglobulin-G (IgG) which suggest that these antibody-producing cells infiltrate the pancreatic islets (Glerchmann et at., 1987, Immunology Today, 8, 167-170).
To date, there does not exist an effective method for inhibiting the disease process. Accordingly, there has been much research to elucidate the pathogenesis of this disease. It is believed that a better understanding of the disease mechanism will result in the development of a method for arresting early pancreatic injury, thus possibly preventing the entire disease process.
In particular, recently this investigation has focused on identifying the specific antigens which result in the production of islet-cell antibodies which are present in the sera of patients who have been recently diagnosed with insulin dependent diabetes mellitus. It is believed that complement fixing islet cell antibodies are highly predictive of active pancreatic beta cell destruction.
Islet-cell antibodies are believed by very few researchers to have pathological significance in this disease since they may represent the initial means of attack on the plasma membrane. The nature of the antigen to which these antibodies bind is not definitively known. However, Brekkeskov et at. (Nature, 1982, 298, 167-168) disclosed that a human islet-cell protein of relative molecular mass 64 kilodaltons now identified as GAD, is precipitated by antibodies found in sen of patients who have been recently diagnosed with Type I diabetes mellitus.
It is believed by some researchers that antibodies directed against the islet-cell membrane and intercellular antigens may be important in the pathogenesis of this disease, while others believe that such antibodies may play no significant role in the disease (Drash et al., Pediatric Clin. North Amer., 1990, 37, 1467-1489). For example, Drash et al. recently suggested that the process which results in islet-cell destruction may be initiated by environmental factors. Id.
Some epidemiological studies have shown that patients expressing Type I human leukocyte antigens (HLA) B-8 and B-15 are more susceptible to diabetes than are patients who do not express these antigens (Codworth et al., Br. Med. J., 1976, 2, 864-867). Other studies also indicate that HLA Class II antigens encoded by DR genes (DR3 and DR4) are also associated with diabetes. Patients with one of such DR antigens have four times greater risk of developing this disease than the general population. Also, patients having both DR antigens have approximately twelve times the risk for developing Type I diabetes mellitus than the general population. HLA DQ8 is even more tightly associated with Type I diabetes.
There also have been hypotheses that link genetic susceptibility to diabetes to immunological conditions which result in the production of cytokines. In fact, there is a large body of research which suggests that cytokines may be responsible for beta cell destruction. Several of the more accepted hypotheses which purport to explain the onset of Type I diabetes mellitus are reviewed as follows.
The "environmental factor hypothesis" proposes that islet cells may initially be damaged by an environmental factor (Trucco et at., Crit, Rev. Immunol., 1989, 201-244). Suspected environmental factors which may damage beta cells include viruses such as coxacklevirus, mumps and rubella, as well as chemicals such as nitrosamines. The gaged beta cells are then believed to release an antigen which is not usually encountered by immunocompetent cells. This antigen becomes what is known as an auto-antigen. Thereafter, a tissue macrophage processes this auto-antigen and presents it to helper T cells in conjunction with an HLA Class II molecule. The helper T cells then induce B lymphocytes to secrete antibodies directed against specific epitopes of the beta-cell antigen These antibodies bind to the beta cell, activating a complement cascade which is believed to result in cytotoxicity. This cytotoxic activity is believed to be supported by cytotoxic T cells which infiltrate the damaged islets and continue to attack the beta cells either directly or via an antibody-dependent response.
A second hypothesis as to the immune mechanism which causes Type I diabetes mellitus was recently set forth by Bottazzo et al (Diabet. Med., 1986, 3, 119-122) and is known as "Bottazzo's Hypothesis". These researchers proposed instead that an environmental stimulus (factor X) causes the beta cell to express Class II molecules (cellular antigens encoded by the HLA-D region such as HLA-DP, HLA-DQ and HLA-DR) which are normally hidden to helper T cells.
This process then continues as in the previous environmental factor hypothesis model, except that specific Class II DR antigens must be present. In particular, DR2 does not allow for the activation of helper T cells whereas DR4 does. Cytotoxic T cells, activated through signals from the helper T cell directly (cell surface antigen encoded by the HLA-A, HLA-B and HLA-C loci) which are expressed on the surface of the beta cell.
A third hypothesis which purports to explain the immune development of Type I diabetes mellitus was also proposed by Trucco et al (Crit. Rev. Immunol., 1989, 201-244). This model suggests that the HLA region is involved in diabetes susceptibility and is located in the HLA DQ locus, in close association with the DR locus on the sixth chromosome. This hypothesis suggests that there is a foreign protein which is processed and presented by CD4-positive acrophage. Helper T cells recognize the antigen which is bound to the expressed Class II molecule. The activated helper T cell then secretes interleukin-2 (IL-2), a cytokine, which stimulates the proliferation of cytotoxic T cells. The activated cytotoxic T cell then expresses the IL-2 receptor and Class II molecules on its cell surface.
The interaction between the CD4 molecules of the helper T cells and the Class II molecules which are expressed on the cytotoxic T cells brings the helper and cytotoxic T cells in contact, causing IL-2 to be effective. Also, B lymphocytes divide and produce specific antibodies with the help of activate helper T cells. Other cytokines product by activate helper T cells stimulate the expression of Class I and Class II molecules at the beta-cell's surface, thus providing targets for CD8-positive cytotoxic T cells and for CD4-positive helper T cells, respectively. The major cytokines that are released during this autoimmune cascade include IL-1 tumor necrosis (TNF) and gamma interferon (IFN-.gamma.).
The putative role of cytokines and interferons in the development of Type I diabetes mellitus has been substantially reported in the literature. Some of this literature is reviewed as follows.
Researchers have disclosed that both gamma interferon and alpha interferon expression may be used to induce Type I diabetes mellitus in transgenic mice (Cell, 1988, 52, 773 to 782; and Science, 1993, 260, 1942-1946). Transgenic mice which express either of these interferons exhibit inflammatory destruction of pancreatic islets which appeared to suggest that these interferons have a causal relationship in the development of this disease condition.
Also, Campbell et al (Journal Of Clinical Investigation, 1991, 87, 739-742) teach that gamma interferon and IL6 have an essential role in the development of insulin dependent diabetes mellitus. However, there is conflicting research in this area. For example, Kaptur et at, Journal of Interferon Research, 1989, 9, 671-678, teach that gamma interferon does not play a major role in protecting pancreatic beta cells against infection by encephalomyocarditis virus (EMCV-D) and therefore does not appear to be essential in the onset of Type I diabetes mellitus. By contrast, Yoon et at, 1983, Journal of Infect. Dis., 147, 155-159, report that repeated administration of gamma interferon or a gamma interferon inducer reduced the development of diabetes in mice which had been infected with EMCV-D. However, it is subject to some question as to whether viral induced diabetes is an adequate animal model for Type I diabetes mellitus.
Additionally, various research groups have indicated that diabetes may be prevented in animal models of Type I diabetes mellitus by the administration of antibodies to gamma interferon which are purported to inhibit gamma interferon activity. For example, Debray-Sachs et at, Journal of Autoimmunology, 1991, 4, 237-248 and Kay et at, Diabetologia, 1991, 34, 779-785, disclose that anti-gamma interferon antibodies prevent insulitis and diabetes in the non-obese diabetic (NOD) mouse.
Also, Kurschner et al, Journal of Immunology, 1992, 149, 4096-4100, disclose that conjugates of interferon gamma receptor and an immunoglobulin may be used to prevent streptozotocin-induced diabetes in mice.
In vitro effects of gamma interferon have also been studied on pancreatic cells. For example, Sarvetnick et al, 1990, Nature, 346, 844-847 teach that gamma interferon results in an influx of inflammatory cells which causes the progressive destruction of pancreatic islets which is apparently mediated by lymphocytes. Also, Cearns-Spielman et al, Autoimmunity, 1990, 8, 135-142, disclose that gamma interferon increases the susceptibility of murine pancreatic beta cells to lysis by allogeneic cytotoxic T-lymphocytes. Corbett et al, Proceedings of the National Academy of Science, 1993, 90, 1731-1735, further teach that high doses of recombinant IL-1, TNF-alpha and gamma interferon induce the formation of nitric oxides by human islet cells which are purported to mediate the inhibition of insulin secretion of said islets. The authors also report that small doses of these cytokines slightly stimulate insulin secretion.
Recently, the effects of gamma interferon and alpha TNF on human fetal beta cells were studied by Tuch et at, Journal of Clinical Endocrinological Metabolism, 1991, 73, 1044-1050. These researchers disclose that both TNF alpha and interferon gamma function as growth factors for human beta cells. They further hypothesized that the functional immaturity and lack of normal (adult) metabolic activity of human fetal beta cells may act to protect these cells from the normal cytotoxic effects of both of the cytokines.
While the bulk of available research suggests that cytokines, and gamma interferon in particular, comprise a deleterious and possibly causal role in the onset and production of Type I diabetes mellitus, some researchers have proposed the use of cytokines as therapeutic agents for the treatment of Type I diabetes mellitus and/or for treating the symptoms of this disease.
For example, Campbell et al, Journal Of Autoimmunity, 1991, 4, 249-262, disclose that TNF alpha in combination with gamma interferon or TNF alpha by itself acts to reduce the severity of insulitis in NOD mice. They purport that TNF alpha may therefore have anti-diabetic properties similar to IL1. However, they observed no significant difference to blood sugar level after gamma interfereon administration. Moreover, these researchers suggest no therapeutic role for gamma interferon, presumably because gamma interferon had no appreciable effect by itself on insulitis, and further because gamma interferon had no effect on blood sugar levels.
Also, Koivisto et at, Diabetologia, 1984, 27, 193-198, teach that human leukocyte (alpha interferon) administration in patients which have been newly diagnosed with Type I diabetes mellitus, in conjunction with insulin administration, results in no higher remissions than patients who have been treated by conventional insulin therapy. Furthermore, Fabris et al, Lancet, 1992, 340, 548 recently reported a patient that developed Type I diabetes mellitus during leukocyte interferon therapy (for chronic human hepatitis) and hypothesized that this treatment may have enhanced the autoimmune process, although it probably existed to some extent prior to interferon treatment.
Jacob, Chaim, Seminars in Immunology, 1992, 4, 147-154, recently reviewed the effects of cytokines including tumor necrosis factor and gamma interferon in the onset and treatment of autoimmune disorders. The effects of interferon-gamma in the adjuvant arthritis model and in human rheumatoid arthritis were reviewed as well as the effects of TNF in a Type I diabetes mellitus animal model (NOD mice).
While them exist some suggestions in the literature regarding the use of cytokines for the treatment of autoimmune conditions, most future therapies for the treatment of Type I diabetes mellitus are instead aimed at interrupting cytokine production and/or cytokine receptor expression. For example, studies in NOD mice have shown that cyclosporin (which blocks the production of interleukin 2) can prevent this disease, as can rapamycin (which suppresses IL2 or II.4 driven T-cell proliferation). However, to date, the clinical trials using these immunosuppressants have proved disappointing. (Brouhard et at, Cleveland Journal of Medicine, 1992, 59, 629-632).
Therefore, based on the above, it is clear that a better understanding of the effect of cytokines, including gamma interferon, on the onset and progression of Type I diabetes mellitus as well as effective methods for the treatment and/or prevention of Type I diabetes mellitus comprise a substantial need in the art.
Toward this end, the present inventor has surprisingly discovered that the administration of gamma interferon or analogs thereof may be used as an effective method for preventing and/or treating Type I diabetes mellitus. The present invention is especially surprising given that gamma interferon was previously believed by some researchers to comprise a causal relationship in the onset of Type I diabetes mellitus, was reported to result in a deleterious effect to pancreatic beta cells in tissue culture, and further because antibodies which are specific to gamma interferon (which are believed to inhibit gamma interferon activity) have been reported to prevent Type I diabetes mellitus.